"I" personally don't like to see the valve guide area thinned out to the point that the edges are razor sharp. Who knows? A small piece could break off and fall into the cylinder. That would suck. Also.....regarding the finish of the ports. I was once a proponent of the "rough" intake finish myself, but after consulting those who do it for a living and reading their experience, it's NOT the finish, but the port size and shape that makes the determination in flow. The carburetor (or injectors) have the job to atomize fuel. Once it's atomized, it's atomized. It ain't gettin no better. lol